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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use euclid::size::Size2D;
use layers::platform::surface::{NativeDisplay, NativeSurface};
use std::collections::HashMap;
use std::collections::hash_map::Entry::{Occupied, Vacant};
use std::hash::{Hash, Hasher};
/// This is a struct used to store surfaces when they are not in use.
/// The paint task can quickly query for a particular size of surface when it
/// needs it.
pub struct SurfaceMap {
/// A HashMap that stores the Buffers.
map: HashMap<SurfaceKey, SurfaceValue>,
/// The current amount of memory stored by the SurfaceMap's surfaces.
mem: usize,
/// The maximum allowed memory. Unused surfaces will be deleted
/// when this threshold is exceeded.
max_mem: usize,
/// A monotonically increasing counter to track how recently tile sizes were used.
counter: usize,
}
/// A key with which to store surfaces. It is based on the size of the surface.
#[derive(Eq, Copy, Clone)]
struct SurfaceKey([i32; 2]);
impl Hash for SurfaceKey {
fn hash<H: Hasher>(&self, state: &mut H) {
let SurfaceKey(ref bytes) = *self;
bytes.hash(state);
}
}
impl PartialEq for SurfaceKey {
fn eq(&self, other: &SurfaceKey) -> bool {
let SurfaceKey(s) = *self;
let SurfaceKey(o) = *other;
s[0] == o[0] && s[1] == o[1]
}
}
/// Create a key from a given size
impl SurfaceKey {
fn get(input: Size2D<i32>) -> SurfaceKey {
SurfaceKey([input.width, input.height])
}
}
/// A helper struct to keep track of surfaces in the HashMap
struct SurfaceValue {
/// An array of surfaces, all the same size
surfaces: Vec<NativeSurface>,
/// The counter when this size was last requested
last_action: usize,
}
impl SurfaceMap {
// Creates a new SurfaceMap with a given surface limit.
pub fn new(max_mem: usize) -> SurfaceMap {
SurfaceMap {
map: HashMap::new(),
mem: 0,
max_mem: max_mem,
counter: 0,
}
}
pub fn insert_surfaces(&mut self, display: &NativeDisplay, surfaces: Vec<NativeSurface>) {
for surface in surfaces {
self.insert(display, surface);
}
}
/// Insert a new buffer into the map.
pub fn insert(&mut self, display: &NativeDisplay, mut new_surface: NativeSurface) {
let new_key = SurfaceKey::get(new_surface.get_size());
// If all our surfaces are the same size and we're already at our
// memory limit, no need to store this new buffer; just let it drop.
let new_total_memory_usage = self.mem + new_surface.get_memory_usage();
if new_total_memory_usage > self.max_mem && self.map.len() == 1 &&
self.map.contains_key(&new_key) {
new_surface.destroy(display);
return;
}
self.mem = new_total_memory_usage;
new_surface.mark_wont_leak();
// use lazy insertion function to prevent unnecessary allocation
let counter = &self.counter;
match self.map.entry(new_key) {
Occupied(entry) => {
entry.into_mut().surfaces.push(new_surface);
}
Vacant(entry) => {
entry.insert(SurfaceValue {
surfaces: vec!(new_surface),
last_action: *counter,
});
}
}
let mut opt_key: Option<SurfaceKey> = None;
while self.mem > self.max_mem {
let old_key = match opt_key {
Some(key) => key,
None => {
match self.map.iter().min_by(|&(_, x)| x.last_action) {
Some((k, _)) => *k,
None => panic!("SurfaceMap: tried to delete with no elements in map"),
}
}
};
if {
let list = &mut self.map.get_mut(&old_key).unwrap().surfaces;
let mut condemned_surface = list.pop().take().unwrap();
self.mem -= condemned_surface.get_memory_usage();
condemned_surface.destroy(display);
list.is_empty()
}
{ // then
self.map.remove(&old_key); // Don't store empty vectors!
opt_key = None;
} else {
opt_key = Some(old_key);
}
}
}
// Try to find a buffer for the given size.
pub fn find(&mut self, size: Size2D<i32>) -> Option<NativeSurface> {
let mut flag = false; // True if key needs to be popped after retrieval.
let key = SurfaceKey::get(size);
let ret = match self.map.get_mut(&key) {
Some(ref mut surface_val) => {
surface_val.last_action = self.counter;
self.counter += 1;
let surface = surface_val.surfaces.pop().take().unwrap();
self.mem -= surface.get_memory_usage();
if surface_val.surfaces.is_empty() {
flag = true;
}
Some(surface)
}
None => None,
};
if flag {
self.map.remove(&key); // Don't store empty vectors!
}
ret
}
pub fn mem(&self) -> usize {
self.mem
}
}
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